Q: Fuel smell and poor fuel economy

asked by on February 15, 2017

I've noticed my gas life shortening and I smell fuel coming from under the hood. My car starts ok with a little hesitation. It shuts off kind of rough though. I've noticed a strange sound as it idles.

My car has 180000 miles.
My car has an automatic transmission.

Hello, There are a number of things that can cause the fuel smell and poor fuel mileage as you describe. I would start with checking the mass air flow sensor as this is a common component that can become dirty or faulty that can cause the kind of hesitation, fuel smell and poor fuel mileage you describe. This is a unit that reads the outside air intake as it enters the engine and relays this to the engine’s computer. The computer then makes adjustments to the fuel supply to the motor based upon these inputs. When this is not working properly, this causes an imbalance in the air/fuel load that is injected into the motor.

A clogged catalytic converter can also cause this kind of problem. When this happens, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly. When this happens, the engine is forced to work much harder to expel these gases. This often results in the engine bogging down, hesitating, shaking and causing very poor fuel economy.

A clogged or dirty EGR valve may also cause poor fuel mileage. This is a valve that allows unburnt fuel and exhaust gases to be recirculated into the intake manifold in controlled amounts to be burned with the fuel charge in the motor. When the EGR valve is clogged or dirty (this is very common) it may not function properly causing the engine to idle rough, stall at idle speeds, cause the car to get poor fuel mileage, or emit a strong smell of fuel. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle to determine what may be causing your car to perform poorly.

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